In a career spanning more than 30 years, John Pettigrew has seen big changes in the electricity industry. He started out in 1991, working to introduce natural gas-fired power plants to the grid, gradually replacing polluting coal plants. .

Now, once again, he is managing a tectonic shift to an electrified economy that runs on renewable energy like wind and solar power. But these sources of power generation are far trickier to manage than their coal and gas predecessors.

“Effectively, what we’re doing is reconfiguring the whole network,” said Mr. Pettigrew, chief executive of National Grid, which owns and operates the high-voltage electricity grid in England and Wales.

Mr. Pettigrew was emerging from a tunnel nearly 20 miles long that National Grid has bored deep underground at a cost of about 1 billion pounds (about $1.3 billion). The shaft, which workers ride through on bicycles, will carry new cables to feed the power-hungry offices and residential communities of London.

Mr. Pettigrew and his company are in the spotlight these days. The Labour Party government of Prime Minister Keir Starmer, which came to power in July, is taking a close interest in the electric power system, which it sees as a primary vehicle for delivering political and economic goals.

A more robust, versatile grid will be crucial not only for tackling climate change but for securing Britain’s place on the cutting edge of artificial intelligence, which requires vast amounts of power to run data centers.

The government aims for 95 percent of Britain’s electricity to come from what it calls “clean” sources like wind and nuclear by the end of the decade, up from about 60 percent in 2023. At the same time, demand for electric power is expected to surge.

“We haven’t started to think about how seriously we need to invest in our core infrastructures for the resilience of our economy in a digital world,” Dieter Helm, a professor of economic policy at the University of Oxford, said in a recent podcast.

The price tag for an electricity system that can handle such changes is around £40 billion a year from 2025 to 2030, according to the government. National Grid alone has filed documents with regulators to spend as much as £35 billion over five years.

National Grid was founded in 1990 when the Central Electricity Generating Board, which managed the power network in England and Wales, was broken up in an era of privatization. (The company, which is listed in London, also has a large business managing power networks in the United States.) Mr. Pettigrew has run National Grid for nearly a decade, but he may be facing his greatest challenge, industry experts say.

“I think there’s a big question about how can they build rapidly enough all this new infrastructure at the same time as maintaining the same standards,” said Edgar Goddard, a former National Grid executive and now a director of EPNC Energy, a consulting firm.

An electrified economy will require a highly reliable grid for a host of reasons, including national security, analysts say. At the same time, critics of renewable energy say that relying on sources of power like wind and solar, which are by their nature variable, creates new challenges for the system.

On April 2, a parliamentary hearing on the Heathrow outage became a venue for executives from the airport and power companies politely dodging blame. Electricity executives said that there was sufficient power available. Alice Delahunty, National Grid’s president for transmission and a key aide to Mr. Pettigrew, conceded that the fast-changing demands being made of the power system called for a careful rethinking about it’s resilience.

Britain’s high-voltage network, like those of other countries, used to be relatively simple, bringing electricity from large generating plants — often near where the coal burned in them was mined — to London and other cities.

Now Mr. Pettigrew is extending National Grid’s tentacles toward the coasts, sometimes through scenic areas, to capture new sources of electricity like the giant offshore wind farms now being built in the North Sea.

He also must make sure the system can carry a lot more power.

Demand for electricity, which has been sluggish in recent years, is expected to double in the coming decades as more drivers take the wheel of electric vehicles and data centers spring up to handle everything from financial services to artificial intelligence.

There is already a long line of wind farms, battery storage facilities and data centers waiting to hook up to the grid — sometimes with increasing frustration. “Their connections process is very poor,” James Basden, a founder of a power storage company called Zenobe Energy, said about the large power operators.

A small industry has sprung up to advise companies on how to navigate the gauntlet of securing access to the grid. “We’re seeing huge demand,” said Simon Gallagher, managing director of UK Network Services, one of those firms.

The government is betting that installing swaths of wind turbines — both on land and in the seas off Britain’s coasts — as well as thousands of miles of high-voltage cables will attract investment, nurture clean tech jobs and reduce the country’s vulnerability to price swings in energy like those that occurred after Russia’s 2022 invasion of Ukraine that led to reduced supplies of natural gas.

Since that invasion, high energy costs have been a major issue in Britain and across Europe, where governments have been forced to spend heavily to help households pay their bills.

Some analysts, though, say the huge costs of installing a new energy system may at least partly cancel out the low running costs of wind and solar. “There’s a lot of infrastructure that needs to be built and that’s going to be paid either by taxes or electricity prices,” said Chris Wilkinson, a senior analyst at Rystad Energy, a consulting firm.

Much is at stake for Britain and the wider clean energy industry. If the government’s ambitions prove unrealistic, that could be a blow to the industry, which is already under fire from the Trump administration in the United States.

It certainly won’t be easy to rewire Britain. National Grid is working on 17 large power projects. Some of the schemes involve laying cables for miles offshore to transfer electricity from clusters of wind farms planned for Scottish waters to consumers in England.

Others involve new power lines marching through rural areas on enormous pylons — a prospect that riles up local residents against both the government and National Grid.

The government is taking advantage of its large majority in Parliament to push through legislation curbing the options of opponents of power projects to pursue what it recently called “meritless cases” in court. The government is also planning to offer up to £2500 in compensation over 10 years to people living near the new pylons.

It often takes many years to push projects through the planning system in Britain. Mr. Pettigrew says that process needs to speed up so that Britain can meet its green energy goals.

To achieve anything close to the government’s targets will require an abrupt change in Britain’s leisurely pace of building infrastructure. Offshore wind capacity, for instance, will need to roughly triple. To bring this clean power to consumers will require adding around 3,400 miles of new power lines to the grid, about twice as much as was constructed in the previous decade.

“The way I would describe it is that everybody has to play their part perfectly over the next five years,” Mr. Pettigrew said.